Elongate plastic member and method and apparatus for providing structural strength to same

ABSTRACT

An apparatus for increasing the rigidity of an elongate plastic member having a groove formed in an exterior surface thereof is an elongate metal reinforcing member, preferably having a generally T-shaped cross section, the member being adapted for placement into the groove so that the member fits snugly into the groove. An improved elongate plastic member has a reinforcing member formed, preferably by roll forming, into a rigid structure, preferably having a substantially T-shaped cross-section when viewed end-on. The insert fits tightly within a groove in the plastic portion of the improved elongate plastic member. An elongate plastic member is provided structural strength by forming in the plastic member a groove adapted so that a reinforcing member will fit tightly within the groove and then placing a reinforcing member into the groove.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] Not applicable.

COPYRIGHT STATEMENT

[0002] Not applicable.

FEDERAL RESEARCH STATEMENT

[0003] Not applicable.

BACKGROUND OF THE INVENTION

[0004] 1. Field of the Invention

[0005] The invention relates to an improved plastic lumber and to an improved method and apparatus for providing structural strength to plastic lumber. Plastic lumber is a class of building materials that are made from plastic and intended to be used for the same purposes and applications as traditional wooden lumber. Plastic lumber provides several advantages over wooden lumber. Plastic lumber is less susceptible than wood to rotting, splitting, moisture absorption, mildew, termite and rodent attacks, and fire.

[0006] 2. Description of the Related Art

[0007] Plastic lumber is superior to traditional wooden lumber in most respects, but plastic lumber is not as stiff or strong (particularly in sheer, bending, and torsion) as wooden lumber. Therefore, plastic lumber is insufficient for some applications because it is not rigid enough to withstand a required loading without suffering failure or excessive deformation.

[0008] For example, plastic lumber has been used in building fences. Plastic lumber works well for the fence boards or planks, the (typically) vertical members that make up most of the body of a fence. However, plastic lumber lacks the rigidity to serve as either fence posts (the vertical supports for the fence which are typically anchored in the ground) or the fence rails (the typically horizontal load-bearing members to which the fence pickets or fence boards are attached).

[0009] One method of resolving the problem created by the lack of rigidity of plastic lumber is to use plastic lumber for non-load-bearing portions of a given structure while using traditional wooden lumber for load-bearing members. However, building a structure using wooden load-bearing members with plastic lumber non-load-bearing members reduces the benefits of the longer life of plastic lumber because the wooden load-bearing members of the construction will fail at the end of their normal life span, requiring the structure to be rebuilt or repaired just as often as an all-wood construction. Accordingly, it is an object of the current invention to reinforce plastic lumber structural members so that load-bearing elements of structures can be constructed of plastic lumber.

[0010] The assembly of structures made from unreinforced plastic lumber requires different procedures and different tools from those used for the construction of structures made from wooden lumber. A further object of this invention is to provide an improved plastic lumber that will allow contractors to construct objects from plastic lumber using the same tools and procedures that they currently use with wooden lumber.

[0011] Plastic lumber may be reinforced by adding chemical or composite reinforcements to the plastic lumber material. However, these approaches are costly and often do not add sufficient rigidity to make the plastic lumber suitable for use in load-bearing members. Accordingly, it is an object of this invention to provide a cost-effective improved plastic lumber and a cost-effective method and apparatus for increasing the rigidity of plastic lumber.

[0012] Plastic lumber members have been reinforced by using metallic inserts. U.S. Pat. No. 3,767,504 to Singleton describes a method of reinforcing a plastic bar member by providing a rigid metal reinforcing strip having a rectangular cross section, forming a groove in the plastic bar, positioning the metal reinforcing member in the groove, placing a strip of plastic over the reinforcing bar and applying beads of molten plastic over the strip to bond to the strip and to each side of the groove by melting and solidifying in sequence.

[0013] U.S. Pat. No. 5,862,642 to Erwin describes a reinforced composite deck post that comprises an elongate, hollow, extruded plastic shell, the plastic shell having a rectangular cross-section. The plastic shell has an upper end and a lower end and has a notch formed therein adjacent to the lower end for receiving a wood joist of a wood deck. The reinforced composite deck post also includes an elongate metal stiffening member positioned within the plastic shell and rigidly secured thereto, generally adjacent to the upper end of the plastic shell. Upper and lower shim means are positioned within the plastic shell adjacent to the metal stiffening member for securing the metal stiffening member to the plastic shell. Erwin discloses a metal reinforcing member that is trapezoidal in cross-section and is manufactured by bending or otherwise forming flat sheet metal, preferably G-90 galvanized steel with a wall thickness of 0.100 inches, into the desired shape. The reinforcing member is rigidly secured to an inside face of the plastic outer shell by wedges or shims. The invention also includes a crush-resistant insert used to prevent the metal stiffening member from being crushed when the bottom end of the reinforced post is attached to a joist.

[0014] There remains a need for an improved metallic insert for plastic lumber that allows ease of assembly and an uncomplicated, yet effective method for stiffening plastic lumber.

SUMMARY OF INVENTION

[0015] The present invention provides an improved apparatus and method for increasing the rigidity of an elongate plastic member, and also provides an improved plastic lumber having increased structural rigidity.

[0016] According to the present invention there is provided a reinforcing member, preferably having a substantially T-shaped cross-section when viewed end-on, that is, when viewed perpendicular to the long or principal axis of the reinforcing member. The reinforcing member preferably comprises a thin sheet of metal bent or otherwise formed into a “T” shape. The T-shaped metal insert is inserted into a corresponding groove or cut-out, preferably also T-shaped, in one side of a length of plastic lumber. When inserted, the reinforcing member fits snugly in the groove and imparts rigidity to the plastic member. The plastic member can be plastic lumber used in fence posts or fence rails or can be plastic members used in other load-bearing applications.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017]FIG. 1 is an end view of a reinforcing member according to a preferred embodiment of the invention.

[0018]FIG. 2 is an end view of a reinforcing member according to an alternative embodiment of the invention.

[0019]FIG. 3 shows an end view of a plastic member according to the invention, showing a preferred embodiment of a reinforcing member inserted into a corresponding groove in the plastic member.

DETAILED DESCRIPTION OF THE INVENTION

[0020] Referring more specifically to the several views of the drawing, FIG. 1 discloses reinforcing member 1 which embodies the present invention, and which comprises a generally rectangular sheet of reinforcing material, preferably metal that has been formed, preferably by roll forming, into a rigid structure having a substantially T-shaped cross-section when viewed end-on. The T-shaped structure defines segments S1 through S6 having corresponding lengths L1 through L6. The segments are continuous, but adjacent segments define angles a1 through a5.

[0021] The reinforcing material is preferably 16 gauge galvanized steel. Alternatively, the reinforcing material can be other metals, such as copper, aluminum or tin, can be hard plastic, or can be a composite material. The key properties are rigidity, with some resiliency or memory, sufficient to allow an insert comprising the reinforcing material to be snugly inserted into a corresponding grooved portion of a plastic member. Any reinforcing material used may be any cross-sectional shape that will accommodate a 180 degree bend. Stainless steel, aluminum, cooper, and reinforced fiberglass are some alternatives.

[0022] The dimensions of the reinforcing material are typically {fraction (1/16)} inch thick, 1⅛ inch high, and of a width sufficient to span most or all of the plastic member into which an insert made from the material is inserted. A principal axis is defined along the width. For a typical application, as shown in FIG. 3, plastic member 3 has a grooved or cut-off portion 4, defining a T-shaped groove into which a reinforcing insert 1 is inserted. Insert 1 has member segments S5 and S6 forming an approximately 3 degree to an approximately 5 degree angle so that, once inserted, the outer corner of end p2 digs into inner wall 5 of plastic member 3, resulting in a tight fit and impeding easy removal of insert 1.

[0023] In an alternative embodiment shown in FIG. 2, insert 2 is formed so that segment S6 overlaps segment S1. Segments S5 and S6 of insert 2 can likewise form an angle so that the outer corner of end p2 digs into inner wall 5 of plastic member 3, resulting in a tight fit and impeding easy removal of insert 2.

[0024] The dimensions of the grooved or cut-out portion 4 of plastic member 3 can be selected so that insert 1 or insert 2 can be pressed into groove or cut-out portion 4 to form a press fit. preferably, groove or cut-out portion 4 is sized so that when insert 1 or insert 2 is placed into position, the insert is recessed within plastic member 3 so that no portion of the insert protrudes beyond a plane formed on an exterior surface of the plastic member.

[0025] The plastic member can be plastic lumber sized for use as fence posts or fence rails. The plastic member can comprise recycled waste thermoplastic resin, or, alternatively, cellulose fiber aggregate.

[0026] Persons or ordinary skill in the art can appreciate that the invention disclosed and claimed herein is not restricted to the embodiments shown and described, and that various modifications are within the true scope of the invention as claimed. 

1. A method for increasing rigidity of an elongate plastic member, comprising: supplying a metal reinforcing member having a principal axis and a cross-section perpendicular to the principal axis; forming in an exterior surface of the elongate plastic member a groove adapted so that the reinforcing member fits tightly within the groove; and placing the reinforcing member within the groove.
 2. A method for increasing rigidity of an elongate plastic member according to claim 1, wherein said cross-section is substantially T-shaped.
 3. A method for increasing rigidity of an elongate plastic member according to claim 2, wherein the cross-section of the reinforcing member defines a shape having: a thickness t; a starting point p1; a first segment of length L1, the first segment joining the starting point p1 to a first angle a1; a second segment of length L2, the second segment being essentially perpendicular to the first segment and joining first angle a1 and a second angle a2; a third segment of length L3, L3 being approximately equal to two times the length (L2+t), the third segment running parallel and adjacent to the second segment and joining second angle a2 and a third angle a3; a fourth segment of length L4, L4 being approximately equal to L2, the fourth segment running parallel and adjacent to the third segment and joining third angle a3 and a fourth angle a4; a fifth segment of length L5, L5 being greater than L1, the fifth segment running parallel and adjacent to the first segment and joining fourth angle a4 and a fifth angle a5; and a sixth segment of length L6, the sixth segment running parallel and adjacent to the first segment and joining fifth angle a5 and an end point p2.
 4. A method for increasing the rigidity of an elongate plastic member according to claim 2, wherein the cross-section of the reinforcing member defines a shape having: a thickness t; a starting point p1; a first segment of length L1, the first segment joining the starting point p1 to a first angle a1; a second segment of length L2, the second segment being essentially perpendicular to the first segment and joining first angle a1 and a second angle a2; a third segment of length L3, L3 being approximately equal to twice the length (L2+t), the third segment running parallel and adjacent to the second segment and joining second angle a2 and a third angle a3; a fourth segment of length L4, L4 being approximately equal to L2, the fourth segment running parallel and adjacent to the third segment and joining third angle a3 and a fourth angle a4; a fifth segment of length L5, L5 being greater than L1, the fifth segment running parallel and adjacent to the first segment and joining fourth angle a4 and a fifth angle a5; and a sixth segment of length L6, L6 being slightly less than L5 minus L1, the sixth segment running adjacent to the fifth segment and forming an angle with said fifth segment of approximately 3 to approximately 5 degrees at a5, and joining fifth angle a5 and an end point p2.
 5. A method for increasing the rigidity of an elongate plastic member according to claim 2, wherein the groove is T-shaped and is adapted such that when the reinforcing member is placed in position in the groove, the base of the cross-section of the reinforcing member is recessed with respect to the surface of the elongate plastic member.
 6. A method for increasing the rigidity of an elongate plastic member according to claim 3, wherein the reinforcing member is formed from sheet metal.
 7. A method for increasing the rigidity of an elongate plastic member according to claim 4, wherein the reinforcing member is formed from sheet metal.
 8. A method for increasing the rigidity of an elongate plastic member according to claim 6, wherein the reinforcing member is formed from sheet metal by a process comprising rolling.
 9. A method for increasing the rigidity of an elongate plastic member according to claim 7, wherein the reinforcing member is formed from sheet metal that is formed by a process comprising rolling.
 10. A method for reinforcing an elongate plastic member according to claim 4, further comprising the step of incorporating the reinforced elongate plastic member into a structure.
 11. A method of reinforcing an elongate plastic member according to claim 10, wherein the reinforced plastic member is incorporated into the structure so as to bear a load.
 12. A method of reinforcing an elongate plastic member according to claim 11, wherein the structure is a fence.
 13. A method of reinforcing an elongate plastic member according to claim 12, wherein the reinforced elongate plastic member forms at least one fence post.
 14. A method of reinforcing an elongate plastic member according to claim 12, wherein the reinforced elongate plastic member forms at least one segment of the fence rail.
 15. A method of reinforcing an elongate plastic member according to claim 10, wherein the plastic member is made from recycled plastic material.
 16. A method of reinforcing an elongate plastic member according to claim 10, wherein the metal reinforcing member is made of steel.
 17. An apparatus for increasing the rigidity of an elongate plastic member having a groove formed in an exterior surface thereof, comprising: an elongate metal member, the member being adapted for placement into the groove so that the member fits snugly into the groove.
 18. An apparatus for increasing the rigidity of an elongate plastic member according to claim 17, wherein the elongate metal member has a cross-section perpendicular to its principal axis, the cross-section being generally T-shaped.
 19. An apparatus for increasing the rigidity of an elongate plastic member according to claim 18, wherein the elongate metal member has a cross-section perpendicular to its principal axis, the cross-section defining a shape having: a thickness t; a starting point p1; a first segment of length L1, the first segment joining the starting point p1 to a first angle a1; a second segment of length L2, the second segment being essentially perpendicular to the first segment and joining first angle a1 and second angle a2; a third segment of length L3, L3 being approximately equal to twice the length (L2+t), the third segment running parallel and adjacent to the second segment and joining second angle a2 and a third angle a3; a fourth segment of length L4, L4 being approximately equal to L2, the fourth segment running parallel and adjacent to the third segment and joining third angle a3 and a fourth angle a4; a fifth segment of length L5, L5 being greater than L1, the fifth segment running parallel and adjacent to the first segment and joining fourth angle a4 and a fifth angle a5; and a sixth segment of length L6, the sixth segment running parallel and adjacent to the first segment and joining fifth angle a5 and an end point p2.
 20. An apparatus for increasing the rigidity of an elongate plastic member according to claim 18, wherein the elongate member has a cross-section perpendicular to its principal axis, the cross-section defining a shape having: a thickness t; a starting point p1; a first segment of length L1, the first segment joining the starting point p1 to a first angle a1; a second segment of length L2, the second segment being essentially perpendicular to the first segment and joining first angle a1 and a second angle a2; a third segment of length L3, L3 being approximately equal to two times the length (L2+t), the third segment running parallel and adjacent to the second segment and joining second angle a2 and a third angle a3; a fourth segment of length L4, L4 being approximately equal to L2, the fourth segment running parallel and adjacent to the third segment and joining third angle a3 and a fourth angle a4; a fifth segment of length L5, L5 being greater than L1, the fifth segment running parallel and adjacent to the first segment and joining fourth angle a4 and a fifth angle a5; and a sixth segment of length L6, L6 being slightly less than L5 minus L1, the sixth segment running adjacent to the fifth segment and forming with said fifth segment an angle of approximately 3 to approximately 5 degrees at a5, and joining fifth angle a5 and an end point p2.
 21. An apparatus for increasing the rigidity of an elongate plastic member according to claim 20, wherein the reinforcing member is formed from sheet metal.
 22. An apparatus for increasing the rigidity of an elongate plastic member according to claim 21, wherein the reinforcing member is formed from sheet metal that is formed by a process comprising rolling.
 23. An apparatus for increasing the rigidity of an elongate plastic member according to claim 22, wherein the apparatus is made of steel.
 24. An improved elongate plastic member having a principal axis, comprising: an elongate plastic member having a groove in one exterior surface thereof parallel to the principal axis of the elongate plastic member; and an elongate metal member adapted for insertion into and inserted into the groove so that the elongate metal member fits tightly within the groove.
 25. An improved elongate plastic member according to claim 24, wherein said reinforcing member has a cross-section perpendicular to its principal axis, the cross-section being generally T-shaped.
 26. An improved elongate plastic member according to claim 25, wherein the elongate metal member has a cross-section perpendicular to its principal axis, the cross-section defining a shape having: a thickness t; a starting point p1; a first segment of length L1, the first segment joining the starting point p1 to a first angle a1; a second segment of length L2, the second segment being essentially perpendicular to the first segment and joining first angle a1 and a second angle a2; a third segment of length L3, L3 being approximately equal to twice the length (L2+t), the third segment running parallel and adjacent to the second segment and joining second angle a2 and a third angle a3; a fourth segment of length L4, L4 being approximately equal to L2, the fourth segment running parallel and adjacent to the third segment and joining third angle a3 and a fourth angle a4; a fifth segment of length L5, L5 being greater than L1, the fifth segment running parallel and adjacent to the first segment and joining fourth angle a4 and a fifth angle a5; and a sixth segment of length L6, the sixth segment running parallel and adjacent to the first segment and adjoining fifth angle a5 and an end point p2.
 27. An improved elongate plastic member according to claim 25, wherein the elongate metal member has a cross-section perpendicular to its principal axis, the cross-section defining a shape having: a thickness t; a starting point p1; a first segment of length L1, the first segment joining the starting point p1 to a first angle a1; a second segment of length L2, the second segment being essentially perpendicular to the first segment and joining first angle a1 and a second angle a2; a third segment of length L3, L3 being approximately equal to twice the length (L2+t), the third segment running parallel and adjacent to the second segment and joining second angle a2 and a third angle a3; a fourth segment of length L4, L4 being approximately equal to L2, the fourth segment running parallel and adjacent to the third segment and joining third angle a3 and a fourth angle a4; a fifth segment of length L5, L5 being greater than L1, the fifth segment running parallel and adjacent to the first segment and joining fourth angle a4 and a fifth angle a5; and a sixth segment of length L6, L6 being less than L5 minus L1, the sixth segment running adjacent to the fifth segment and forming an angle with said fifth segment of approximately 3 to approximately 5 degrees, and joining fifth angle a5 and an end point p2.
 28. An improved elongate plastic member according to claim 28, wherein the reinforcing member is formed from sheet metal.
 29. An improved elongate plastic member according to claim 28, wherein the reinforcing member is formed by a process comprising rolling. 